Modern electronic product, such as notebook computer, hand-held computer, tablet computer, mobile phone, smart phone, wearable gadget (e.g., wrest watch or glasses), digital camera, digital camcorder, navigator, or game console, etc., demands wireless functionality compliant to one or more wireless standards, and therefore needs antenna operable at compliant RF band(s) with compliant performances and/or characteristics to properly receive and/or transmit wireless signals. For example, a product demanding telecommunication functionality of LTE standard requires antenna operable at two RF bands respectively covering 700 MHz and 1800/1900 MHz. However, it is difficult to satisfy both product design (industry and/or mechanical design) and antenna design.
Antenna design aims to ensure compliance of antenna performances and/or characteristics, such as band location, bandwidth, return loss, efficiency, and/or impedance, etc. On the other hand, product design aims to enhance user experience. For example, a popular and prevailing design trend of wearable product like smart watch is to adopt metallic case (housing), and also demands compact size (smaller than smart phone) for user's comfort of wearing. While dimensions of antenna depend on wavelengths of compliant RF band(s), maintaining compact size constrains vacancy left for embedding antenna in the case. Furthermore, enclosing antenna inside metallic case seriously degrades antenna performances. Although cutting slot(s) on metallic case may ease antenna design, but is not preferred for compact-sized product like smart watch, because the slot(s) will look unpleasantly conspicuous on compact-sized product, and therefore become eyesore to impact product appearance.
Some smart watch designs implement antenna on watchband instead of the main case where watch panel locates, but suffer degraded antenna performances since the antenna is therefore closer to user skin, which is potentially conductive. Also, placing antenna on watchband is disadvantageous for user customization and personalization which rely on swapping watchbands.